Fiduciary Accounting Services LLC | 128 followers on LinkedIn. Specialized Accountings for Trusts, Estates, and Conservatorships | Fiduciary Accounting Services, LLC (FAS) is a specialized accounting firm that partners with trustees, attorneys, financial institutions and others with fiduciary accounting needs. Our singular objective is to be the premier provider of accounting for trusts, estates, and conservatorships in California. Since our inception in 2007, we’ve been meeting the challenge of tracking and documenting complicated financial transactions into a simple, straightforward process – providing you with actionable information.